I have a combi boiler, which provides ample hot water. However, when i need to use the shower i find that to get a good warm shower i need to turn on a cold tap so the shower is warmer. The shower is not elcetric, it is a plunge shower and it is on the same floor as the boiler, about 3-4 meters away. The same is when we run baths if we turn the tap up quite high more cold water comes out than hot, even when we have had the boiler on for about 30 mins. Is this a pressure issue?

A combi is a very simple piece of kit.
You put cold water in at one end, its heated and it comes out hot.
The action is based on raising the temperature of cold water to a comfortable shower level.
If it is summer and the water in the mains is warm, it is easy for the combi to raise the water temperature to a satisfactory level.
If it is freezing outside, the boiler has to work harder.
So there it is, too much too cold water and the boiler cannot cope!

There is a control on the boiler to increase the temperature inside the boiler, has someone turned it down during the summer?
You can also close the inlet water valve on the boiler to reduce the amount of freezing water going in...this will also raise the water temperature.

The boiler is baxi combi boiler, I also noticed that the bath taps also have the same issue, if i turn the hot tap up too far then more cold than hot water comes out. If i leave it just above a trickle the water is really hot. I tend to turn the heating on before we have a shower so that it heats quicker so i do not think that is an issue. the hot water is turned up to maximum temp aswell.

There are quite a few valves underneath the boiler, i know which one increases the pressure, but im not too sure what one would be the inlet valve

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